The studio behind the PG-13 movie, 20th Century Fox, is more cautious, saying it will likely haul in $95 million to $100 million over the holiday weekend. The studio said "X-Men" would face strong competition from "Godzilla," which opened big last weekend.

The studio also noted that with "Godzilla," "Captain America: The Winter Soldier" and "The Amazing Spider-Man 2" there has been no shortage of big-budget action flick releases recently.

"X-Men: Days of Future Past," the seventh film in the series that Singer kicked off in 2000, marks the big-screen return of Marvel characters Wolverine (Hugh Jackman), Mystique (Jennifer Lawrence), Professor X (Patrick Stewart) and Magneto (Ian McKellen). In "Days of Future Past" the X-Men of the original trilogy send the claw-wielding, fast-healing Wolverine back in time to join forces with their younger selves (previously seen in 2011's "X-Men: First Class").

Singer, whose last "X-Men" directing effort was "X2: X-Men United" in 2003, has elicited praise from critics for his handling of the complicated plot, as evidenced by a score of around 90% "fresh" from Rotten Tomatoes. Singer pulled out of the promotional campaign for the new movie after a lawsuit filed in April accused him of sexually abusing a teenager in the late 1990s.

The last time an "X-Men" film opened with more than $100 million was 2006's "X-Men: The Last Stand," which also debuted over a Memorial Day weekend and amassed nearly $123 million over four days on its way to a $459-million worldwide gross.

"X-Men," which cost $200 million to make, will need to clear $95 million to top "Captain America: The Winter Soldier" as the biggest opening of the year so far. The red-white-and-blue-clad super-soldier has grossed more than $250 million domestically so far, along with more than $450 million overseas, for a worldwide total exceeding $700 million.

Moviegoers will have a romantic alternative to the superhero and rampaging reptilian fare in the form of "Blended," a PG-13 Warner Bros. comedy starring Adam Sandler and Drew Barrymore. The poorly reviewed rom-com, which had a production budget of $45 million, is likely to gross $30 million through Monday.